Hydraulic mechanism



Oct. 5, 1943. Y c, DE GANAHL 2,331,108

HYDRAUL I G MECHANI SM Filed July 10, 1940 5 Sheets-Sheet l l INVENTOR 5 4 eaq l/ ATTORNEYS Oct. 5, 1943. (3. DE GANAHL HYDRAULIC MECHANISM 5 Sheets-Sheet 3 Filed July 10, 1940 ATTORN EY5 Oct. 5, 1943.

c. DE GANAHL 2,331,108

HYDRAULIC MECHANISM Filed July 10, 1940 5 Sheets-Sheet 4 INVENTOR (2 04 66! 46/ ATTORN EYS Oct. 5, 1943. c, DE GANAHL 2,331,108

HYDRAULIC MECHAN I SM Filed July 10, 1940 5 Sheets-Sheet 5 NVENTOR (.qr/ d 40 ATTORNEYS Patented Get. 5, 1943 HYDRAULIC MECHANISM Carl de Ganahl, Bristol, Pa., assignor, by mesne assignments, to Reconstruction Finance Corporation Application July 10, 1940, Serial No. 344,764

8 Claims.

This invention relates to hydraulic actuating mechanism, and particularly to devices adapted to control such mechanism and to effect certain safeguards in the operation, especially with respect to the completion of any operation which is initiated and the avoidance of false operations, which might endanger the mechanism or the apparatus in which it is installed.

The invention is designed more specifically to facilitate the operation of hydraulic mechanism installed in aeroplanes, for example mechanism for actuating landing gear, flaps and other movable elements which must be constantly under the control of the operator. Hydraulically operated mechanism of the type described is now commonly utilized in aeroplanes, but has been subject to certain obvious defects in respect to the certainty of operation, especially the completion of the operation after initiation thereof. There has been noted also a tendency, particularly among student and inexperienced pilots of aeroplanes, to initiate the wrong operation at critical points. For example, pilots sometimes cause the landing gear to be raised when it should remain lowered while taxiing, thus sometimes involving themselves in relatively serious accidents. i

It is the object of the present invention to provide hydraulic mechanism capable of actuating various elements in an aeroplane or other device with controlling means therefor designed to ensure completion of the desired operation when it has been initiated, the mechanism being thereupon automatically released.

Another objeet of the invention is the provision of mechanism which can be released manually by the operator if the automatic control fails for any reason.

Another objectof the invention is the provision of a plurality of controlling devices connected in series but so arranged that if actuated in unison only one will become effective until the operation controlled thereby has been completed, whereupon the other will automatically perform its function, thereby avoiding reduction of the pressure on the medium employed to actuate the mechanism to the point where it Would become ineffective for the purpose.

Another object of the invention is the provision of a limit device whereby the intended movement of any particular elementor elements such as the flaps of an aeroplane may be set and controlled, the automatic operation being com- Still another object of the invention is the provision of means preventing operation of certain parts of the mechanism when the conditions are such that such operation should be avoided, for example lifting of the landing gear while the gear is in contact'withthe ground or other support.

Other objects and advantages of the invention will be apparent as it is better understood by reference to the following specification and accompanying drawings, in which Fig. l is a side elevation of a valve and the controlling mechanism therefor adapted to be embodiedin a hydraulic system for actuating any desired element;

Fig. 2 is a bottom plan view of the structure shown in Fig. 1; v

Fig. 3 is a longitudinal section on the line 3-3 of Fig. 2;

Fig.- 4 is a similar section on Fig. 3;

Fig. 5 is a section on the line 5-5 of Fig. 1;

Fig. 6 is a general diagrammatic representation showing embodiment of two valves in a hydraulic system controlling the landing gear and flaps of an aeroplane, it being understood that this drawing is illustrative only and that the invention is not limited to the particular applications shown; y

Fig. 7 is a diagrammatic view illustrating the application of safety mechanism which under certhe line 4-4 of tain circumstances prevents actuation of the I. It Will be understoodthat thev landing gear is such as is commonly employed in aeroplanes, and that it is supported in'the usual manner under the wings of the plane. For purposes of illustration, the two struts 5 are shown in different positions. Each is actuated bya piston rod 8 connected to a piston 9 ina cylinder l0 which is pivoted at I I. The pistons 9 are double acting, so that the landing gear can be lifted or moved to supporting position as desiredby supplying fluid under pressure to the respective cylinders l0 under suitable control as hereinafter described. I

Also shown in Fig. 6 is the representation of a flap l2 pivotally supported in the usual manner and provided with levers I3, one of which is connected by a link l4 to a bell crank l5, the other being connected to the bell crank l5 by links I 8, I1 and iii. The bell crank I5 is connected to a piston rod I9, carrying a piston 20 in a cylinder 2|. The piston 26 is likewise double acting, so that the flap may be moved in either direction by supplying fluid under pressure to either end of the cylinder. It is to be understood that any movable element may be connected similarly through suitable linkage to a piston which may be actuated under control of the operator.

The fluid is maintained in a reservoir 22 and is withdrawn through pipe 23 to a constant volume hydraulic pump 24 which delivers the fluid through a pipe 25 to the control valve 26. A similar valve 21, supplied with fluid through the pipe 28, controls the movement of the flaps or of any other element which is to be moved under control of the operator. The fluid ordinarily is not under pressure and merely circulates through the system, returning to the reservoir. When, however, it is directed to one or more of the pistons and meets resistance, pressure is built up rapidly by the pump 24 and the fluid pressure is transmitted to the piston to actuate it in the desired direction.

The valve 26 and the companion valve 21 are shown in more detail in Figs. 1-5 inclusive, to which reference is now made. An instrument panel 29 is provided to which the valve 26 is secured by bolts 29'. A bracket 39 on the panel pivotally supports the operating lever 3| having a handle 32 which is shown in the drawings in its uppermost position, indicating actuating of the valve to lift the landing gear. A quadrant 33 is provided with a notch 34 and a tooth 35 on the lever 3|, and engages the notch when the handle is in the off or neutral position. cated, from that position it may be moved also to a position corresponding to the lowering of the landing gear.

The lever 3| is provided with a fork 36 engaging a pin 31 on the valve rod 38 which extends through the valve and housing and is provided with lands 39 at intervals. Within the valve housing which is made preferably of an aluminum alloy is a nitricast iron sleeve 40 through which four circumferentially disposed holes are drilled at intervals corresponding with recesses 40 in the housing. The valve housing is provided at one side with a port 4| which is adapted to be connected to the pipe 25 through which fluid is supplied from the hydraulic pump 24. The fluid passes through a passage 42 and, with the valve disposed in the position indicated in Figs. 3 and 4, the fluid passes to a chamber 43 and thence through a port 44 adapted to be connected to a pipe 45 leading to both cylinders ill, a branch pipe 46 afl'ording connection to one of the cylinders. The fluid thus enters the ends of the cylinders to force the pistons in the proper direction to raise the landing gear. The fluid thus supplied to the cylinders builds up pressure and actuates the pistons until the landing gear has been lifted. The fluid from the opposite side of the two pistons 9 is returned through pipes 41 and 48, the fluid passing thence through a pipe 49 to the valve 26 which is connected to a port 50 which allows the fluid to pass through a passage 56, thence through a port 52 which is connected to a pipe 53 leading to the reservoir 22. Thus, the fluid is returned to the reservoir.

The operation as above described could be accomplished by moving the handle 32 to the position shown in Figs. 3 and 4. and at the completion of the operation moving the handle back to the neutral position in which the circulating fluid enters through the port 4i and escapes through As indithe port 8| without causing the actuating of any mechanism, the operation at this stage being merely circulation of the fluid from the reservoir through both valves and back without developing any pressure until it is desired to actuate some part of the mechanism. To avoid the necessity for such manual operation, provision is made to hold the valve in actuating position when it has moved to that position, and to return it only when the desired operation is completed. To eflect this purpose, the valve rod 38 is provided with an extension 54, within a housing 55. The extension 54 carries flanges 56 and 51 adapted to engage a switch lever 58 controlling the movement of a switch having two points 59 and 60 (Fig. 6). The extension 54 also carries two loose washers 6| and 62 which are separated by a spring 63. Detents 64 (Fig. 5) are pivoted at 65 and are adapted to project into the path of the washers 6| and 62 so that when the valve rod 38 is moved to the limit of its travel in either direction, one of the detents 64 will engage the corresponding washer 6| or 62 and hold the valve rod in the selected position, so that the fluid builds up pressure and is effective at the selected point or points to complete the desired operation.

To release the detents, a solenoid 66 is supported on the housing and is provided with a plunger 61 (Fig. 5) which is normally held in the position indicated by a spring 68 which biases the detents 64 to retain the valve mechanism in the selected position. When the solenoid 66 is energized, the plunger 61 is lifted and engages the tail 69 of the detents, thereby withdrawing them, whereupon the spring 63 returns the valve to its normal or neutral position.

In order that the valve may be released only at the completion of the intended operation, I provide an electrical circuit with a source of power 10 which is connected by a conductor 1| to the solenoid 66. The other terminal of the solenoid is connected by a conductor 12 to the switch arm 58 which is actuated by movement of the valve to engage one or the other of the switch points 59 and 60. The switch points and 59 are connected by conductors 13 and 14 to limit switchesv 16 and 15 disposed adjacent and adapted to be actuated by flanges 11 on the piston rods-8. The limit switches 15 and 16 for each of the two sides of the landing gear are connected in series by conductors 18 and 19 and by a return conductor 80, which is connected to the source of power 10. The switches 15 and 16 normally remain in open position. Thus, when the valve has been moved to the point where fluid is delivered to the cylinders ID, to lift the landing gear as indicated in Fig. 6, the connection from the source of fluid pressure will be maintained until the landing gear has been raised and the limit switches 16 have been closed by the flange 11 moving to latched position, as shown at the lefthand side of Fig. 6, whereupon the solenoid 66 will become effective to release the valve which will return to normal position.

Where one or more valves adapted to actuate mechanism for different functions are connected in series as indicated in Fig. 6, the second valve may be actuated and will be locked in the actuating position. However, the pipe 28 which supplies fluid to the second valve is connected to a port 8| of the first valve and cannot receive the fluid until the first valve has completed its function and has returned to normal position, whereupon fluid entering through the port 4| will be directed through the port 8| and pipe 28 to the second valve which will then permit the flow of fluid through a pipe 02 to the cylinder 21, the fluid from the opposite side of piston 20 returning thence through a conduit 83 to the valve and through a pipe 84 to the reservoir 22.

The mechanism of the valve 21 is identical with that of the valve 26, and need not be described, therefore; in detail. However, in order to permit movement of an element, for example a flap, to any desired degree, and to release the valve when the particular movement has been completed, I provide a limit switch 85 having an indicator 86. By moving the indicator to the desired point, a contact 81 is moved over a plurality of points 08 connected by conductors 89 to contacts 90 dis" posed in the path of the piston rod IS. A single limit switch 9I is likewise provided in the path of the piston rod IS. The contact 59 is connected by a conductor 92 to the switch 85, and a conductor 93 connects the contact 60 with the limit switch 9I Return conductors 94 and 95 are connected to the source of power I0. When the flap is to be moved down, thelimit of the desired movement may be set on the indicator, and when the piston has traveled to the extent desired, 'it will automatically close the circuit and release the valve, which will return to normal position.

Similarly, when the flap is to be moved up, the

valve will be released automatically, when the flap has reached its uppermost position, by limit switch 9i.

Should the electrical mechanism fail for any reason, it is still possible for the operator to return the valve manually to neutral position.

The washers GI and 62, beingloose on the ex to any movable elements, and that any number of valves may be disposed in series and so connected that they will function serially when two or more of the operating handles are moved to either of the operating positions, and that each valve will be retained in'iopera-tive position until the desired operation has been completed, wmrer upon each valve will be released and returned to normal position. Thus, by way of illustration, the operator could set the valve 26 to lower the landing gear and at the same time set the valve 2! and the indicator 86 to effect movement of the flaps. The landing gearwould immediately move to landing position, and when the operation was completed the valve 26 would be released and the valve 21 would then come into operation to effect movement of the flaps. Obviously, any desired arrangement of the valves and of the relation of cifective operation thereof could be set up, and other valves and mechanism controlled thereby could be added to the, arrangement illustrated in Fig. 6. Any desired combination, therefore, can be utilized, since the invention rests primarily in the valve and the mechanism whereby the valve is held in operative position until completion of the particular desired function.

pens that a nervous pilot may undertake to raise the landing gear of a plane while the plane is standing with the wheels in contact with a suping', the result may be disastrous.

As hereinbefore indicated, it sometimes hap-" (I landing gear.

porting surface. Obviously, if the plane is mov- To avoid this possibility, the mechanism hereinbefore described may be provided with an additional control through either electrical or hydraulic connections, so that the valve controlling the hydraulic mechanism cannot be actuated when the wheels are supporting the weight of the plane.

Referring to Fig. 7, the strut 5 carrying the wheel 6 consists, as usual, of telescoping elements. The struts are provided with the usual nutcracker joint to prevent the wheels from turning, consisting of pivoted arms 96 and 91. When the strut is compressed, a cam 98 on the arm 91 disengages a switch 99 to open a circuit from a source of current I00 through a conductor I0i, conductor I02, switch I03, conductor I04, solenoid I05 and conductor I06. The switch I03 is disposed adjacent the end of the valve rod 38 so that ing gear.

In Fig. 8, the same result is accomplishedby connecting a by-pass pipe I08 to the line which supplies fluid under pressure to the cylinder I0 to lift the landing gear. This pipe is connected to a valve chamber I09 supported on the strut 5; A valve seat I I0-is normally closed by a valve II I under pressure of a spring H2. A return line II3 permits the .fluid to return to the reservoir 22. The nut-cracker. joint, consisting of pivoted arms H4 and. I I5, is provided as usual. When the strut is compressed, a cam H6 is brought into engagement with the valve stem I I1, lifting the valve against the spring and permitting the fluid to by-pass without efiecting movement of the actuating piston. Thus, when the plane is standing or moving. with the wheels in contact with a surface, the valve III will be lifted from its seat and the fluid supplied through the valve 25 will be ineffective to cause operation of the However, when the plane is not supported on the landing gear, the valve III will be closed and the landing gear may then be raised in the manner hereinbefore described.

The mechanism as set forth, and particularly the valve with its controlling devices, affords practical and safe means forv moving the various elements of an aeroplane or of any other similar mechanism in which hydraulic operation is desirable. The operator is assured in every instance when the valve is moved to the limit of its travel in either direction, that the operation will be completed and the valve will be returned automatically. I

Various changes may be made in the details of construction and of operation of the various parts of the mechanism without departing from the invention or sacrificing the advantages thereof.

I claim: 1. In an hydraulic actuating mechanism for movableelements, a reservoir for a fluid medium, a pump, means for translating hydraulic pressure into movement, a valve normally permitting circulation of the fluid medium when the valve is in neutral position and adapted when actuated. to

direct the fluidmedium to the translating means,

and adapted to be moved thereby, and electrically controlled means associated with the valve to return it automatically to neutral position when the movement of the element is completed, including a latch, electromagnetic means to release the latch, a limit switch in the path of movement of the element, an electrical circuit connecting the switch and electromagnetic means and a spring to actuate the valve when released.

2, In an hydraulic actuating mechanism for movable elements, a reservoir for a fluid medium, a pump, means for translating hydraulic pressure into movement, a valve normally permitting circulation of the fluid medium when the valve is in neutral position and adapted when actuated to direct the fluid medium to the translating means, an element connected to the translating means and adapted to be moved thereby, and electrically controlled means associated with the valve to return it automatically to neutral position when the movement of the element is completed, including a latch, electromagnetic means to release the latch, limit switches in the path of movement of the element, electrical circuits connecting the limit switches and the electromagnetic means. selector means permitting the closure of a particular circuit when the element has moved into engagement with the selected limit switch, and a spring to actuate the valve when released.

3. In an hydraulic actuating mechanism for a wheel strut of the landing gear of an aeroplane, a reservoir for a fluid medium, a pump, means for translating hydraulic pressure into movement, a valve normally permitting circulation of the fluid medium when the valve is in neutral position and adapted when actuated to direct the fluid medium to the translating means, a wheel strut of the landing gear of an aeroplane connected to the translating means and adapted to be raised and lowered thereby, means associated with the valve to return it automatically to neutral position when the movement of the wheel strut in one direction is completed, and means for rendering the fluid medium ineffective to operate the translating means when the wheel strut is in its lowered position and in contact with the ground and supporting the weight of the aeroplane.

4. In an hydraulic actuating mechanism for a wheel strut of the landing gear of an aeroplane, a reservoir for a fluid medium, a pump, means for translating hydraulic pressure into movement, a valve normally permitting circulation of the fluid medium when the valve is in neutral position and adapted when actuated to direct the fluid medium to the translating means, a wheel strut of the landing gear of an aeroplane connected to the translating means and adapted to be raised and lowered thereby, means associated with the valve to return it automatically to neutral position when the movement of the wheel strut in one direction is completed, and means for rendering the fluid medium ineffective to operate the translating means when the wheel strut is in its lowered position and in contact with the ground and supporting the weight of the aeroplane, including means for blocking actuation of the valve.

5. In an hydraulic actuating mechanism for movable elements, a reservoir for a fluid medium, a pump, means for translating hydraulic pressure into movement, a valve normally permitting circulation of the fluid medium when the valve is in neutral position and adapted when actuated to direct the fluid medium to the translating means, an element connected to the translating means and adapted to be moved thereby, means associated with the valve to return it automatically to neutral position when the movement of the element is completed, and means for rendering the fluid medium which is directed to the translating means inefiective to operate the translating means when said element is under load, including means for relieving the fluid pressure on the translating means and returning the fluid to the reservoir.

6. In an hydraulic actuating mechanism for movable elements, a reservoir for a fluid medium, a pump, means for translating hydraulic pressure into movement, a valve normally permitting circulation of the fluid medium when the valve is in neutral position and adapted when actuated to direct the fluid medium to the translating means, an element adapted to be put under load, said element being connected to the translating meansand adapted to be moved thereby, means associated with the valve to return it automati cally to neutral position when the movement of the element is completed, and means to prevent flow of the fluid medium to the translating means when said element is under load, including electrical means for blocking actuation ofthe valve.

'7. In a device of the character described, a wheel strut of the landing gear of an aeroplane, means for raising and lowering the wheel strut, and electrically controlled means associated with the means for raising and lowering the wheel strut for preventing the wheel strut from being raised when it is under load including a latch, electromagnetic means to release the latch, a switch operable by movement of a part of the raising and lowering means, and an electrical circuit connecting the switch and electromagnetic means.

8. In a device of the character described, a wheel strut of the landing gear of an aeroplane, means for raising and lowering said wheel strut including a power translating member, an element connected to said translating member and adapted to be moved thereby, and electrically controlled means associated with the means for raising and lowering the wheel strut for preventing the wheel strut from being raised when it is under load including a latch, electromagnetic means to release the latch, a switch in the path of movement of the element connected to the translating member and an electrical circuit connecting the switch and electromagnetic means.

CARL DE GANAHL. 

